Stably accessing octave-spanning microresonator frequency combs in the soliton regime

Area of Science:

• Photonics
• Optical Engineering
• Materials Science

Background:

• Microresonator frequency combs are key for optical frequency synthesis and timekeeping.
• Soliton states with broad spectral bandwidths are crucial for self-referencing but are complicated by thermo-optic dispersion.
• Existing methods often require fast pump control to stabilize solitons in platforms like Si3N4.

Purpose of the Study:

• To demonstrate a simplified method for accessing broadband soliton states in microresonator frequency combs.
• To overcome the limitations imposed by thermo-optic dispersion using slow pump laser frequency tuning.
• To provide a theoretical framework explaining the observed phenomena.

Main Methods:

• Experimental demonstration of octave-spanning soliton frequency combs in Si3N4 microresonators.
• Utilizing slow pump laser frequency tuning, significantly slower than thermal dynamics.
• Development of a simplified two-step theoretical analysis incorporating thermo-optic dispersion.
• Numerical simulations based on the Lugiato-Lefever equation.

Main Results:

• Successful generation of octave-spanning soliton frequency combs in Si3N4 microresonators.
• Demonstration of multi-soliton states near 40 mW and single-soliton states near 120 mW pump power.
• Validation of the simplified analysis model against experimental and simulation results.
• Explanation of how adjacent mode families can mitigate thermal requirements.

Conclusions:

• Broadband soliton states can be accessed in microresonator frequency combs with simple, slow pump laser tuning, bypassing the need for fast active control.
• The developed model accurately describes the access to soliton states under thermo-optic dispersion.
• This work simplifies the architecture for low size, weight, and power optical frequency synthesis systems.